1. Field of the Invention
The invention relates to synthetic polar lubricating fluids derived from hydrocarbon compounds and a method for their synthesis.
2. Discussion of the Prior Art
Conventional lubricating fluids can be prepared by combining saturated hydrocarbons with an additive package having constituents which impart favorable properties to lubricating fluids. In particular, they help reduce friction between moving parts, reduce metal reactivity and corrosion, and prevent formation of gum and varnish. The compositions of additive packages are well known and comprise constituents such as those disclosed in "Lubrication and Lubricants." Kirk-Othmer-Encyclopedia of Chemical Technology, 3rd Ed., Vol. 14, pages 490-496. However, to solubilize the additives, substantial quantities of polar compounds must be added. For example, in the past, adipate esters such as bis-tridecanol adipate have been added in amounts of about 20% by weight.
When one adds such large amounts of material into a lubricant, properties such as seal swell, viscometry and oxidation stability become a concern. Seal swell measures the ability of a lubricant to swell a seal, thus enhancing its sealing function. Oxidative stability of a lubricant represents the lubricant's resistance to oxidation and its tendency to form gum and sediment. The viscometric properties concern the viscosity and viscosity index of the material. When materials deficient in these properties are added in large amounts, the lubricant's effectiveness will be impaired.
In consideration of the above, the polar solubilizing agents usually add seal swell capacity, but may not have viscometric properties or resistance to oxidation comparable to that of the basestock. By adding the solubilizing agent, these properties will be impaired. Furthermore, most of these polar materials, such as the adipates, are expensive, and it would be desirable to produce a lubricant in a more economical fashion.
The present invention provides a high molecular weight, aliphatic lubricant which has sufficient polarity to adequately dissolve additive packages without the addition of solubilizing agents such as adipate esters. As a result of hydroformylation, the lubricant molecules contain hydroxy or ester groups which are responsible for the polarity of the fluid.
In the past low molecular weight aliphatics having hydroxy groups or esters have been produced as lubricating fluids. Furthermore, it is known that low molecular weight olefins can be hydroformylated at about 100.degree. C. to produce an aldehyde. The subsequent hydrogenation of the aldehyde to produce a primary alcohol is also known. (see U.S. Pat. No. 4,658,053). This process involves two steps and it would be easier, and more economical, if the lubricating fluid could be produced in one step.